Gas discharge device and circuit therefor



GAS DISCHARGE DEVICE AND CIRCUIT THEREFOR Filed July 5, 1940 y electronemission temperature.

Patented` June 30, 1942 oFFlcE l GAS DISCHARGE DEVICE AND CIRCUITTHEREFOR Samuel Ruben, New Rochelle, N. Application July 5, 194i),Serial No. 344,031 2 claims'. '(01. 17e-'.120

This invention relates to a gas discharge device and specically to anelectric lamp of the fluorescent type capable of directly starting andoperating on a' 120 volt alternating current line without the use ofelectro-mechanical 'control structure, which can be economicallymanufactured, and which in combination with the circuit to be described,operates 'on low commercial alternating current lines without anauxiliary starting device.

Other objects will be apparent as the disclosure proceeds and from thedrawing which shows a Viiuorescent tube and circuit embodying the'invention.

In this invention I utilize a` lamp structure of the type described inmy prior and co-pending application -above referred to, the lamppreferably being in tubular form and having end electrode assemblies,each comprising an oxidecoated electron emitting filament and acooperating electrode which may be in rod form, the discharge betweenthe electrodes of .each assembly, heating the oxide coated filaments tothermionic emission temperature.

In the prior art, where cold starting means have been applied, as forexample, by use of a.- step-up transformer, mechanical interruption ofan inductance, etc., the voltage necessary to discharge through theentire tube length has been such as to cause (by ionic bombardment)rapid destruction of the electrode elements. In the present"inventio`,due to' close spacing between the electrodes effecting the ignitiondischarge, this destructive factor is limited.

In my new arrangement, ionic discharge asu semblies each consisting of athermionic emission element, preferably in filament form, and

ionized atmosphere in the electrode discharge area, allow a readydischarge of the line voltage through the tube without raising thevolt'- age applied tothe tube for eiiecting the: discharge, the linecurrent discharged through the tube being limited by an nductance.

While the method and apparatus described are particularly suited to thefluorescent type of tubes, they can be used with other'types ofgasdischarge tubes. V

In order to further describe the invention, referenceis made to theaccompanying drawingin which is shown an enclosed glass tube I, of 15watt size, coated with a fluorescent material, such as silicateof zinc,cadmium, beryllium or other combinations known to the art. At one end ofthe tube is rod electrode 2 which extends through low mass coiledfilament 3, formed of 2 mil tungsten wire coiled to a length of 21/2inches with 200 turns to the inch, then coated with a mixture ofstrontium and barium oxides in/the manner well known to the art. At; the

opposite end of the tube is a similar electrode assembly, the rod 5.`being similar to rod 2 and filament 6 'being similar to lament 3.Insulator tube 4 of Isolantite or similar material covers part of rod 2so as to confine the Adischarge between electrcdes 2 and 3 to the end ofthe as.- sembly and provide rapid direct heating of the electronemitting coiled filament. Insulator tube 1 performs a similar functionin respect to rod 5 and filament 6.

Condenser 8 of 3A mfd. capacity is connected across mfd. condenser 9,which is in series with rod and lament 5 and 6. As the voltage isdeveloped across condenser 9 connected across alternating cur'ntline""'l2 in series witli"'5700 ohm impedance Il, the connection ofcapacia cooperating element, preferably in' rod form,

are mounted at each end of the tube. An inductance is connected inseries with a condenser to provide the ignition voltage for one pair ofelectrodes. the voltage' being obtained across the inductance. Ignitionvoltage for the other pair of electrodes is 4obtained across thiscondenser,

land the current discharge is limited by a condenser or other impedancein series with these electrodes. The ionic' discharge between the rodand filament electrodes heats the iilamentto The electron emlssivity-ofthe lament when hot, plus the applied to the electrodes 2 and 3 as isapplied Y to the electrodes 5 and 6 due to their connection -about 1500ohms or an inductance impedance where emciency is not the major factor.vductance I0, having an. impedance of 300 ohms at 0.3 ampere, connectedin series with filament 3 and the line, serves to limit the currentdis-A charged through the length. of the tube. A cathe tube.

discharge and thus increase the radiation actival tion of thefluorescent coating on the wall of In operation, when voltage isapplied, there is an ionic discharge between the rod and lamentelectrodes at the ends of the tube which ionizes the end areas. 'rirefilament becoming heated, allows `a low voltage to be maintained betweenthese electrodes, and due to the effect of the heated iilaments and theionized discharge between the electrodes of each end assembly, a dis--charge takes place throughout the length of the tube, the voltagedropping to approximately. 60 volts. After starting, the capacitances 8vand 9 serve to limit the current applied to the end electrodeassemblies. Condenser 9 also serves the added function of allowing thevoltage across inductance I I to reach a value greater than the linevoltage or approach a resonant condition thereby -providing ignitionvoltages across the opposite pairs of electrodes. Thus, by varying theratio of the inductance II to the capacitance 9, voltage greater thanthe line voltage can be applied to the electrodes, thereby avoiding thenecessity of critical spacing or critical gas pressure.V The electricalcharacteristics of the end assembly de `termine the extent of resonance,i! any, in the 'circuit and is dependent upon the electrode materials,gas pressure and spacing of electrodes, some combinations discharging atvoltages below theline voltage.

The electron emitting electrodes of the tube should be of small mass andpreferably of the alkaline oxides coated filament type` so as to becapable of instantaneous heating to thermionic emission temperature. Fora watt lamp of 18 inch length and 1 inch diameter, a coiled 2 miltungsten wire weighingv milligrams has been been found satisfactory.'I'he size and weight ot the iilament will naturally be determined bythe connected to the line comprising an inductance and a seriescapacitance, one electrode assembly being connected to said inductanceand the other electrode assembly connected to said capacitance, withcurrent-limiting means to limit the discharge from said capacitance.

2. In combination, an electric gaseous discharge device comprising asealed tube, a gaseous atmosphere within said tube, an ionic-dischargecouple at each end ofthe tube, each couple comf prising a thermionicelectron emitting iilament and a cooperating electrode, an alternatingcurrent line, an inductance in shuntwith -the elec' trodes of oneof'said couples, the iilament of 'said couple and one terminal of saidinductance being connected to oneside of said line, the other terminalof said inductance and the cooperating electrode of said couple beingconnected to a terminal of a capacitance, the other terminal of thecapacitance being connected to the other side o! said line, said otherside of the line being connected to the iilament of the other couplethrough an inductance in series therewith, the cooperating electrode ofsaid other couple being connected to a terminal of a current-limitingmeans, the other terminal of which is connected to said capacitance andto the cooperating electrode of the other couple.

` SAMUEL' RUBEN.

